The private pilot was practicing crop-dusting maneuvers near Opelousas, Louisiana, when the engine lost total power. He made a forced landing in an open, muddy field.
The Grumman G164 nosed over and sustained substantial damage.
Post-accident examination of the engine revealed that two of three bolts that secured the left magneto had come loose and were missing.
The safety wire was broken, and the Sims coupling was heavily damaged.
The magneto could easily be moved around, which disrupted the spark timing and resulted in a total loss of power.
Probable cause: The loss of two securing bolts that allowed the left magneto to move around, which disrupted the spark timing and resulted in the engine losing total power.
NTSB Identification: CEN18LA357
This August 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
